The present invention relates to a method and system for controlling the operation of electric loads with high reliability.
With the progress of electronic circuits in the automotive industry, for instance, various kinds of electronic equipment (electric loads) have been adapted for use with their respective control devices by which they are driven. In case any one of these control devices develops trouble, it is to be desired that such a control device is backed up to keep the relevant electric load operating in view of safety and the like.
The known backup practice is to provide a standby control device for emergency use in addition to what is used regularly.
As the prior art backup means, moreover, there are those other than the control devices described above as follows:
In an engine drive refrigeration apparatus as disclosed in Japanese Patent Laid-Open No. 113267/1988, there is provided a generator whose function is switchable from power generation to electromotion in a system for transmitting power to the engine and a compressor. When the engine as a power source fails in that case, the power transmission system is switched so that the generator is used as a motor to back up the power source.
In the prior art described in Japanese Patent Laid-Open No. 95121/1974, a plurality of loads are alternately operated by a motor for their common use.
In the proposed prior art of controlling the operation of pumps according to Japanese Patent Laid-Open No. 84318/1989, the priority order is first given to a plurality of operating pumps for regular use and when one of them fails to operate, any one of the remaining pumps is selected from among them and designated for backing up what is out of order in accordance with the priority order.
In the prior art backups as disclosed in Japanese Patent Laid-Open Nos. 113267/1988, 95121/1974, 84318/1989 and the like, those examples include using the generator as a motor by mechanically switching the function of the power transmission system and otherwise designating an electric load which can be substituted for the inoperative from among those for regular use. However, it still remains infeasible to deal with the control device which is out of order.
Consequently, any measure taken to cope with the electric load control device which has developed trouble is to use a standby control so as to keep the electric load operating.
Notwithstanding the use of such standby controls would result in an increase in the number of components like control devices, thus increasing cost. As automobiles can afford only a small space, which tends to restrict the installation of standby control devices, there is still room for improvement in the prior art.